David Petraeus: A retired US general who was named head of the CIA in 2011. He admitted having an affair with Paula Broadwell and stepped down as director of the agency last Friday.

Paula Broadwell: She first met Gen Petraeus six years ago and later became his biographer. The married, mother-of-two published "All In: The Education of General David Petraeus" earlier this year.

Jill Kelley: An unpaid social liaison at MacDill Air Force Base in Tampa, Florida. She reported receiving harassing emails to the FBI and their subsequent investigation unearthed the affair between Gen Petraeus and Mrs Broadwell.

Gen John Allen: A four-star general who has been nominated as the new Nato supreme allied commander for Europe. The FBI has uncovered some 30,000 pages of emails between him and Mrs Kelley.

Senator Dianne Feinstein: The Senate Intelligence Committee chairwoman has said she will investigate the FBI's handling of the scandal, focusing on why the matter was not shared earlier with Congress.

The unnamed FBI agent: Jill Kelley turned to him to complain that she was receiving anonymous messages, falsely accusing her of inappropriate flirting with Gen Petraeus and investigators then began the routine probe that led to the discovery of the general's relationship with Paula Broadwell. The agent was reportedly obsessed with Mrs Kelley and later leaked details of the investigation to Eric Cantor.

Eric Cantor: The House Majority Leader was first informed by an FBI employee about the investigation into Gen Petraeus. He passed the information on to FBI Director Robert Mueller but did not inform fellow House leaders.

James Clapper: The director of national intelligence was advised during the week of the election of the investigation into Gen Petraeus. Mr Clapper notified the Obama administration the day after the election.